2018年10月28日(日) 12:49 Matt Ranostay <[email protected]>:
>
> On Sat, Oct 20, 2018 at 7:26 AM Akinobu Mita <[email protected]> wrote:
> >
> > Add macro to compare two v4l2_fract values in v4l2 common internal API.
> > The same macro FRACT_CMP() is used by vivid and bcm2835-camera. This just
> > renames it to V4L2_FRACT_COMPARE in order to avoid namespace collision.
> >
> > Cc: Matt Ranostay <[email protected]>
> > Cc: Sakari Ailus <[email protected]>
> > Cc: Hans Verkuil <[email protected]>
> > Cc: Mauro Carvalho Chehab <[email protected]>
> > Acked-by: Sakari Ailus <[email protected]>
> > Signed-off-by: Akinobu Mita <[email protected]>
> > ---
> > * v4
> > - No changes from v3
> >
> > include/media/v4l2-common.h | 5 +++++
> > 1 file changed, 5 insertions(+)
> >
> > diff --git a/include/media/v4l2-common.h b/include/media/v4l2-common.h
> > index cdc87ec..eafb8a3 100644
> > --- a/include/media/v4l2-common.h
> > +++ b/include/media/v4l2-common.h
> > @@ -384,4 +384,9 @@ int v4l2_g_parm_cap(struct video_device *vdev,
> > int v4l2_s_parm_cap(struct video_device *vdev,
> > struct v4l2_subdev *sd, struct v4l2_streamparm *a);
> >
> > +/* Compare two v4l2_fract structs */
> > +#define V4L2_FRACT_COMPARE(a, OP, b) \
> > + ((u64)(a).numerator * (b).denominator OP \
> > + (u64)(b).numerator * (a).denominator)
> > +
>
> Noticed a few issues today when testing another thermal camera that
> can do 0.5 fps to 64 fps with this macro..
I expect your new thermal camera's frame_intervals will be something
like below.
static const struct v4l2_fract frame_intervals[] = {
{ 1, 64 }, /* 64 fps */
{ 1, 4 }, /* 4 fps */
{ 1, 2 }, /* 2 fps */
{ 2, 1 }, /* 0.5 fps */
};
> 1) This can have collision easily when numerator and denominators
> multiplied have the same product, example is 0.5hz and 2hz have the
> same output as 2
I think V4L2_FRACT_COMPARE() can correctly compare with 0.5hz and 2hz.
V4L2_FRACT_COMPARE({ 1, 2 }, <=, { 2, 1 }); // --> true
V4L2_FRACT_COMPARE({ 2, 1 }, <=, { 1, 2 }); //--> false
> 2) Also this doesn't reduce fractions so I am seeing 4000000 compared
> with 4 for instance with a 4hz frame interval.
I think this works fine, too.
V4L2_FRACT_COMPARE({ 1, 4000000 }, <=, { 1, 4 }); //--> true
V4L2_FRACT_COMPARE({ 1, 4 }, <=, { 1, 4000000 }); //--> false
Or, do I misunderstand your problem?
